New to solar - bought RV with battery/solar

I bought my 2017 Bighorn RV and it came with the following batteries and solar listed further below. I am trying to determine what the system is capable of and the condition of the batteries.
The lead acid flooded batteries are from 2017 so 6 years old. Is there a way to check how much life is left to determine if they are due for replacement? Also, would AGM 200ah be a good upgrade? How do I determine if I really need 4 x 200ah batteries with a 2000W inverter? How do I determine how long it would take to recharge the batteries with the two solar panels? I imagine there are some equations that I need to answer these questions.
We are planning a cross country trip so will have 5 to 7 days on the road not plugging into shore power. We will be sleeping overnight on the road and will need some power for lights, microwave, coffee pot. I am guessing running an AC unit is not possible.
Thanks!

1) GoPower GP-SW2000 2000W inverter
2) 2 Solar Monocrystalline panels 160W each (9.14A max current)
3) 4 6v Batteries - lead acid flood 200ah each - 105min @ 75 amps 210 Ah @ 20 Hr
4) GoPower GP-PWM-30-UL 30A PWM solar controller
5) GoPower GP-SWR-B Pure Sine wave inverter remote
6) Intelli-Power PD-9280 AC to DC converter

The good news is that your batteries may be in good shape. I don't see any corrosion on the battery terminals. Lead acid batteries tend to outgas as they get close to their end of life (at least mine did). However, if they recently were cleaned of all corrosion then clean terminals could be a false negative. To know for sure, you need to use an hydrometer to check the specific gravity of the electrolyte in each cell. Once you check all cells, record the values and keep track of it.

An item that needs to be changed is the way the batteries are wired. Either the positive or the negative cable needs to be moved to the other battery set. The way they're connected now, the batteries on the right are carrying more of the load/charge than the batteries on the left.

You have a 420 Ah battery bank. If you replace the lead acid batteries with LiFePO4, you'll want about the same Ah total, depending on how much power you want to pull per day and how much the solar charge controller can put back in. Your panels will max out at 26 amps.

Running the air conditioning is unlikely, but trying it out would sure test the system!

The PD9280 converter is pretty good for lead acid batteries. I wouldn't use it for LiFePO4. The charge profile, especially the equalization charge, isn't good for LiFePO4.

Be sure you test the system before you go on your trip. Those batteries are a variety. Two of them are six years old, the other two I can't tell.

I had a system with 4 golf cart batteries. The batteries hold about 4 kWh of power, so about 2 kWh max usable, but especially because they are 6 years old, best to budget around 1kWh the first night or two to see how it goes.

I think you should take some time and get to know this system before upgrades. My guess is provided the batteries still work, then more panels, but see how the trip goes. I’m against AGM; they don’t last as long as well maintained flooded lead acid batteries. 4 golf cart batteries would be perfect for my needs where I could watch TV all day long, and turn heat on at night and cook in the microwave for a couple minutes at a time five or six times a day and not worry about killing the batteries, so I would say if you replace them, then four golf cart batteries are a great choice.

Knowing when it is full is better judged parked in the sun with panels having no shade, when the batteries reach a steady voltage measured with no more amps going in. Then that would be a good gauge to check the charge controller readings.

The fact that you have both main leads on the right pair means that pair is going to severely carry more load and charge than the left pair.

You should move all connectors except the one wire that is already connecting the two terminals to the other terminal as indicated OR do it to the positive side instead.

Your interconnects look VERY thin and likely cause substantial voltage loss under heavy loads as that inverter can pull 2000/12/.85 = 196A.

Completely clean off the tops of the batteries.
Check the torque of all connections.
Add enough distilled water in each cell to keep the plates submerged. Do not fill to top.
Fully charge the battery and float for at least two hours.
Fill cells to proper level with distilled water.
Float for 24 hours.

Document:
Each of the 6V voltages
Specific gravity of all 12 cells (suck and expel fluid three times before each reading)

Do not be misled by the 90% reading. Neither the charge controller nor the inverter display have the ability to report an accurate state of charge. These are gross approximations based on voltage.

You can be confident that the battery is fully charged when the battery is at 14.4V and it can be held there with only 4A of current.

I'm with @chrisski. AGM have half the cycle life of decent well-maintained flooded.

sunshine_eggo said:

You should move all connectors except the one wire that is already connecting the two terminals to the other terminal as indicated OR do it to the positive side instead.

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I am having a tough time visualizing this. Are you saying to move all 2 terminal connectors on the right side circled in blue below over to the left terminal as shown?
Also, which interconnect wires are you saying look too thin? What Guage wire do I need?

chrisski said:

4 golf cart batteries

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I am nor familiar with golf cart batteries. How are they different from what I have and why are they better? Can you recommend a golf cart battery brand and amperage rating?

tmaxx said:

Also, which interconnect wires are you saying look too thin? What Guage wire do I need?

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I used 2/0 wire to connect thev6 volt batteries 2s2p, and then used 4/0 from the battery to inverter and busbar.

Question. I know the advice was to get to know his system first, but wouldn't upgrading the pwm scc to an mppt be advisable? That way as he gets to know his system he is getting max possible from his panels.

Johneb said:

but wouldn't upgrading the pwm scc to an mppt be advisable? That way as he gets to know his system he is getting max possible from his panels.

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I'd watch it work for a while before changing to MPPT. This will give OP a basis for comparison.

tmaxx said:

I am nor familiar with golf cart batteries. How are they different from what I have and why are they better?

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Golf Cart batteries are heavy 6v (3 cell, hence the 3 fill ports) deep cycle batts, typically wired in series for 12v. Very common in RVs for decades, and what is shown in the pic. The batts on the right in the pic are actually labeled GC2.

tmaxx said:

I am having a tough time visualizing this. Are you saying to move all 2 terminal connectors on the right side circled in blue below over to the left terminal as shown?

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Cables marked with yellow. EITHER the positive OR the negative need to be moved. Not both.

tmaxx said:

Also, which interconnect wires are you saying look too thin? What Guage wire do I need?

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chrisski said:

I used 2/0 wire to connect thev6 volt batteries 2s2p, and then used 4/0 from the battery to inverter and busbar.

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Concur

Johneb said:

Question. I know the advice was to get to know his system first, but wouldn't upgrading the pwm scc to an mppt be advisable? That way as he gets to know his system he is getting max possible from his panels.

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A 20-25% improvement in array performance into batteries that may be at end of life does not make it to the top of my priority list.

Got really focused on what I saw with the battery bank. Additional questions:

tmaxx said:

The lead acid flooded batteries are from 2017 so 6 years old. Is there a way to check how much life is left to determine if they are due for replacement?

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Pretty much the only one I answered.

tmaxx said:

How do I determine if I really need 4 x 200ah batteries with a 2000W inverter?

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You technically only have 2 210Ah batteries. The batteries to the inverter are 12V not 6V.

So you have 420Ah of batteries.

Ultimately, you determine what your energy needs are based on the items you wish to use and their duration. Below are capacity-based calculations:

Lead acid batteries have less capacity higher the load. Your batteries are rated at 420Ah @ 20h meaning, you'll only get 420Ah when drawing only 420Ah/20h = 21A.

21A * 12V = 252W

Another rating on the battery is their 75A rating for 105 minutes (x2). That means the batteries can deliver 75A for 210 minutes. 75A * 12V = 900W. This is an effective capacity of 75A * 210 minutes * (1 hr / 60 min) = 262Ah - A 38% reduction from rated.

Running the 2000W inverter @ full power (Microwave + absorption fridge) = 196A - nearly 3X the 75A rated current, so at best I'd guess 262Ah to be cut to half again, so 131Ah.

131Ah/196A = 40 minutes

Now... the fun part... lead acid batteries have poor life if you run them below 50%... so every number above needs to be cut in half:

21A/252W load = 10 hours run time
75A/900W load = 1hr 45 minutes
200A/2000W load = 20 minutes

tmaxx said:

How do I determine how long it would take to recharge the batteries with the two solar panels?

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420Ah of 12V batteries have 420*12 = 5040Wh of energy.

Your solar panels are 320W combined.

For flat panels on an RV roof, I would estimate you get 4 max-power equivalent hours of solar, i.e., from sunrise to sunset, the panels will yield 4 * 320W = 1280Wh of energy. This assumes no shading of the panels from trees, buildings or roof items.

5040Wh/1280Wh/day = 3.9 DAYS of charging provided you use no energy at all.

tmaxx said:

I imagine there are some equations that I need to answer these questions.

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Yep.

Power, P = Current, I * Voltage, V

tmaxx said:

We are planning a cross country trip so will have 5 to 7 days on the road not plugging into shore power. We will be sleeping overnight on the road and will need some power for lights, microwave, coffee pot.

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Assuming batteries are in good condition (you've done what I recommended above), if batteries are fully charged, you should be okay for very short uses. Coffee pot must be turned off immediately once brewing is complete. Typical heating elements are 900W, and you don't want it cycling on and off keeping coffee warm. Drink it fast.

tmaxx said:

I am guessing running an AC unit is not possible.

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Not even close.

HRTKD said:

Running the air conditioning is unlikely, but trying it out would sure test the system!

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Startup of a rooftop unit is > 4500W, so I'm dubious. It should be able to drive the fan for air circulation.

HRTKD said:

The PD9280 converter is pretty good for lead acid batteries. I wouldn't use it for LiFePO4. The charge profile, especially the equalization charge, isn't good for LiFePO4.

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The only information I can find is that this is a constant 13.6V unit with no charge phases. I would argue it's marginal for lead-acid unless on shore power for at least 24-48 hours. I would also argue it's marginal for LFP due to low charge voltage.

HRTKD said:

Be sure you test the system before you go on your trip. Those batteries are a variety. Two of them are six years old, the other two I can't tell.

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Agree!

First, Lead Acid batteries are only usable for 1/2 their rated capacity. Depending on how well they have been cared for, they are near or past their end of life.
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One 200a LFP battery will equal your usable capacity, two will double it.
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Second, the poor wiring configuration has added stress to the batteries. I'd bet one pair would test much better than the other pair.
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Third, consider replacing the PWM SCC with MPPT SCC.

sunshine_eggo said:

Cables marked with yellow. EITHER the positive OR the negative need to be moved. Not both.

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Does this look correct now? I moved three negative terminal wires.

I like to use a microwave oven to test a power system to see how things are going.

I use a measuring cup of water and run it for 3 minutes. During this time I watch the battery voltage and if things are getting hot. (just with my hand) Every 30 seconds I write down the battery voltage.

If you do this test when the batteries are brand new and then once / year, it gives an indication of how much they have degraded over time for your specific system. Ideally it should stay above 12 volts ( or 24 volts) for a 24 volt system.

If the inverter kicks off in just 1 - 2 minutes, then that is a pretty good indication that it is time to change the batteries or make other improvements.

I realize that this is not as scientific of test as it could be, but it is a great indicator.
_________

Most likely your solar panels are wired in parallel - so the PWM controller is just fine, especially for overcast conditions. If the panels were wired in series, then it makes sense to switch to MPPT.

Over time, consider to add another panel.

tmaxx said:

Does this look correct now? I moved three negative terminal wires.

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Yep.

Is the gray wire with blue crimp the one that was in the shroud? Looks like you're running out of thread. Is the nut at least fully engaged on 3 threads?

Meant to mention the wingnut. Almost impossible to get those tight enough. Recommend replacing with a hex nut.

Typical threaded terminals should be torqued to about 8ft-lb.

HarryN said:

I like to use a microwave oven to test a power system to see how things are going.

I use a measuring cup of water and run it for 3 minutes. During this time I watch the battery voltage and if things are getting hot. (just with my hand) Every 30 seconds I write down the battery voltage.

If you do this test when the batteries are brand new and then once / year, it gives an indication of how much they have degraded over time for your specific system. Ideally it should stay above 12 volts ( or 24 volts) for a 24 volt system.

If the inverter kicks off in just 1 - 2 minutes, then that is a pretty good indication that it is time to change the batteries or make other improvements.

I realize that this is not as scientific of test as it could be, but it is a great indicator.
_________

Most likely your solar panels are wired in parallel - so the PWM controller is just fine, especially for overcast conditions. If the panels were wired in series, then it makes sense to switch to MPPT.

Over time, consider to add another panel.

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Sounds good to me.

The only thing I would add to this is to ensure the batteries are as fully charged as possible. Either measuring 14.4V at the terminals or leaving on shore power for 48 hours before the test. Make sure you disable solar or shore charging before you do the test.

I know what I'd do, I'd sell the deep cycles and move to LFP before taking the trip. Upgrade to a LFP compatible MPPT and not have to worry about running out of power.

Best thing I ever did was to install LFP and a 3000W Growatt in my truck camper. She gets to blow dry her hair every morning, I get to run the microwave plus the Dometic fridge/freezer runs off the solar. Wife is happy and I'm happy. We don't have to worry about power in the boonies or parked in a tent site (which are cheaper and close to the campground wi fi).

sunshine_eggo said:

Is the gray wire with blue crimp the one that was in the shroud? Looks like you're running out of thread. Is the nut at least fully engaged on 3 threads?

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Yes, the grey wire is in the shroud. I pulled back the shroud to get more room. I moved over from other terminal. As far as thread engagement, I will need to check that and get back. Thanks

tmaxx said:

I am nor familiar with golf cart batteries. How are they different from what I have and why are they better? Can you recommend a golf cart battery brand and amperage rating?

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Trojan T105s 6V deep cycle batteries are used in golf carts & RVs.

Use it for a few times then decide what YOUR camping style is .......and what needs improving

a) If you always go to a campground with 120v hookup ... you won't need to change anything

b) If you want to go off-grid for a weekend ... you still won't need to change stuff

c) More than a weekend off-grid .... look at more solar panels and possible battery upgrade

you can TEST the RV/Trailer at home before taking a trip
Until you know how well your system works ..... take a small 2000 - 25000w generator along with you

Aussieguy said:

Use it for a few times then decide what YOUR camping style is .......and what needs improving

a) If you always go to a campground with 120v hookup ... you won't need to change anything

b) If you want to go off-grid for a weekend ... you still won't need to change stuff

c) More than a weekend off-grid .... look at more solar panels and possible battery upgrade

you can TEST the RV/Trailer at home before taking a trip
Until you know how well your system works ..... take a small 2000 - 25000w generator along with you

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+1

I'll add - Best place to dry camp is at the house disconnected from shore... You don't even need to be in it. Just periodically go outside and use stuff like you would if you were in it. Leave the TV on for a few hours, nuke some soup, etc.

sunshine_eggo said:

+1

I'll add - Best place to dry camp is at the house disconnected from shore... You don't even need to be in it. Just periodically go outside and use stuff like you would if you were in it. Leave the TV on for a few hours, nuke some soup, etc.

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Take a shower too!! I'm troubleshooting a situation where I've blown a fuse on my water pump circuit. Twice, on different occasions when I'm soaping up and have the switch on the shower nozzle off. It's like the gremlins know THE worst time to blow a fuse.

and don't think the microwave will actually heat stuff...... even if the display is lit.
test with a glass of water inside

@tmaxx , it's been four months. How has your system worked?

if you upgrade to lithium batteries, you need to make sure your charger has a lithium profile (the 9280 doesn't, but Progressive Dynamics should have a drop-in replacement)
the SCC needs a lithium profile
you need to protect your alternator as LFP batteries will burn it out
since this is a trailer with probably a 7-pin connector, no need as the current is limited anyway

tmaxx said:

We will be sleeping overnight on the road and will need some power for lights, microwave, coffee pot. I am guessing running an AC unit is not possible.
Thanks!

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Hope his trip went well. If people find this in the future dont forget about the beauty of propane while doing stealth boondocking on the road. Boil water for coffee and any skillet with a lid can cook food like an oven.